squished against the wet tiles. We were walking the perimeter of the Illini Union, on the campus of theUniversity of Illinois at Urbana-

Champaign. It was a stormy night in April, and students sat slumped in leather chairs, hunched over laptops, rain from umbrellas pooling at their feet.

As we walked past, we talked about the Big Stuff, the passing of time, the universe, knowing when to leave a good thing alone and when to meddle. Somehow, it didn't feel pretentious.

“You know, I've always felt like I make movies that play in real time,” he said, “like we're watching these things just happen. Maybe because I've always been self-conscious about time passing and I've always been worried about time. Even as a kid, I was into cosmology, how time relates to galaxies, stuff like that. I thought life was precious, that movies should be about that; that you don't have to be religious to feel it.”

We kept walking.

As he spoke, in somewhat long, quiet monologues, as we moved through that hallway and into a study lounge, it was hard not to imagine Linklater's camera trailing behind, a lengthy, gliding tracking shot that captured everything and not much at all. Then again, a week earlier I had seen “Before Midnight,” Linklater's latest, opening Friday in Chicago, and I was still under its spell. Like “Before Sunrise” (1995) and “Before Sunset” (2004), it's about an American named Jesse and a Parisian named Celine, played by Ethan Hawke and Julie Delpy, and as with those first two films, there are lots of long, unbroken shots of the pair walking, talking. We grow aware of the smallest moments, of every change in their emotional barometric pressure.

It may be the best special effect you see this summer.

Heck, it may be the best special effect of the past two decades, a two-part, three-movie trick perpetrated by a filmmaker and his actors: First, there is the illusion of intimacy, that we've been watching an actual couple all these years, meet, separate, fall in love, grow distant.

“Which is such a special effect,” Delpy told me later. “You have no idea how uncomfortable, though I feel close to him after all these years, it is to have Ethan touching me. I literally have to shut down as Julie! It's like having your breasts touched by a brother.”

The second part of that trick: The illusion of real time passing, of watching life move in miniature.

“Which is in there because Rick, and I probably don't have to tell you this if you have met him, really is obsessed with the clock,” Hawke said on the phone last week. “I mean, ‘School of Rock,' what could be this ordinary kids movie, has classroom scenes shot in one or two long takes. ‘Slacker' takes place in real time, ‘Dazed and Confused' over one night. ‘Waking Life' seems to unfold in what I think is four seconds. This is a filmmaker who has a lot to say about the clock ticking on the wall — and ticking in the back of our heads.”

Indeed, in “Before Sunrise,” Jesse and Celine meet on a train and decide to get off in Vienna, where they spend the night walking the city, getting to know each other and understanding that they will separate when Celine's train arrives in the morning. It's ridiculously romantic. And “Before Sunset” is even more so: The pair meet nine years later in Paris. Jesse is a successful author, and Celine shows up at a book reading. They get reacquainted in the 80 minutes before Jesse must be at the airport and fly back to the United States. In both movies, Jesse and Celine are trying to beat the clock, to get everything said before their time's up.

“Before Midnight” is different. They're a couple now. They have kids. That clock on the wall seems different.

Linklater and I rounded a corner and entered a mostly deserted study lounge. A door slapped open nearby, and a pair of back-packed students stomped in, shaking themselves free of the rain. A splatter flew as we passed, and Linklater winced and smiled. “This place,” he said, “it makes me feel like, ‘Wow, I'm a student still,' then we pass a few students, and I feel like, ‘Wow, no, I am old now. And so much time has passed.'”

Linklater, who is 52 and was in Champaign as part of Roger Ebert's film festival, is a pleasant paradox: a middle-aged filmmaker with shaggy, flyaway '70s hair who could pass for a graduate student, a revered clock-conscious director whose temper is so happenstance that, when he speaks in his mellow Texas drawl, images of Owen Wilson float up.

Hawke told me: “For every movie we made together, there are two that didn't work for whatever reason. We have been in pitch meetings, trying to get people to invest money in scripts, and Rick announces he's honestly not sure if this film will work, that he doesn't even know if making this film is fiscally responsible! He's, like, the opposite of the image of the director as hustler.” Go figure.

With the “Before” movies in particular, Linklater's been working in a patience-requiring tradition that stretches from Francois Truffaut's Antoine Doinel series (which followed the life of a Parisian, played by the same actor across decades) to the recent finale of NBC's “The Office,” which ended on the lines: “There's a lot of beauty in ordinary things. Isn't that kind of the point?”

He has become a master of the cinematic metronome, so keenly attuned that, as I sat through the “Before” films again, it was hard not to be reminded of personal hopes, failures, lost opportunities and the value of what remains, how I am about the same age as Hawke and Delpy, and the development of their characters roughly traces my own, in real time. You recognize the symmetry that occurs, how the series begins with Jesse and Celine witnessing an argument and ends with an epic, already much-buzzed-about argument between Jesse and Celine themselves.

Even Hawke's character, who is 41 in “Midnight,” recalls how at 18 he wrote a letter to his 40-year-old self reminding himself not to fall into the very traps he fell into. Which Hawke actually did: “It was nonsense. You see so many adults lose their idealism, and at 18 you snicker and wonder where it went. I didn't want to be one of those people, so I wrote a letter. Which probably explains a lot about why Rick and I are close.”

Actually, in a way, the series itself is a kind of letter from Linklater to himself. When I asked him the origin of the initial idea for “Before Sunrise,” he shifted uncomfortably, then said something he hasn't said often:

“It's personal and I don't talk about it, but I met a girl in Philadelphia in 1989, and we ended up spending the night walking around, flirting, doing things you would never do now. I was at that stage in life where I was open, so we just walked and got to know each other. I remember, even as we were walking, thinking, ‘This could be a movie. Not the intrigue that happens after people kiss and sleep together, but this, this period of learning about another person.' Which is probably what makes me a boring partner and boyfriend in the real world — throughout history! I'm never quite there for people, I'm never quite present. I'm always somewhere else.”

What happened after? I asked.

“Well, later I was at a film festival in Europe, and I had never left the U.S. before that, and I spent time walking alone around Berlin and Vienna, which is where the Europe settings for the film came from.”

What happened with the girl? I corrected.

“It's pretty sad,” he said.

I waited.

“She died.”

Hawke told me Linklater hasn't been comfortable mentioning this until “extremely recently,” but he and Delpy knew the details: Her name was Amy Lehrhaupt, and she and Linklater met in a toy shop. For a time, they kept in touch by phone but drifted apart as the Austin, Texas-based filmmaker began a serious relationship. He always thought that maybe she would show up at a screening of “Before Sunrise” and realize her influence, but later, after the film was released, he heard from a friend of Lehrhaupt who knew about their walkabout. Lehrhaupt had died in 1994 in a motorcycle accident, a few weeks before the first movie began shooting. If you hang around through the closing credits of “Before Midnight,” you'll see: The film is dedicated to her.

After Linklater said this, I looked around. A few students sat nearby, but no one was eavesdropping. Linklater pointed to their headphones. Indeed, every one wore headphones. “It's a different world,” he said wistfully.

So different that Linklater told me he feels lucky to have made “Before Sunrise” before the encroachment of Facebook, of never having a good reason to lose touch: “A decade later, there would have been no way they lost touch completely or (as is explained in ‘Sunset') missed each other when they tried to reconnect.”

Besides, the series is about the magic of connection and the tenuousness of that connection — “the poetry of attraction,” Linklater calls it. Which is somewhat ironic considering how efficiently these movies are made.

“I come from a musical family and played an instrument my whole life but have never been very good,” Delpy said. “The only people who are good, practice like crazy, so I practiced the clarinet like crazy, and my dad said, ‘Oh, clarinet is so easy.' My point being, even people who know better, who know how hard it is do something flawlessly, can't help forgetting the work involved. The truth of these movies is, they are tediously rehearsed, every detail planned, every overlapping line scripted. It's so precise that it's almost a joke when people think we are acting off the cuff. But every single line in all three of these movies has been written.”

Linklater cast Hawke and Delpy in 1994, then, with them, completely rewrote the screenplay he had. Delpy said they were not credited because screenwriting guild rules gave authorship to the originators (Linklater and a friend, screenwriter Kim Krizan) and were never seriously challenged.

“Now the way it works,” Linklater said, “is me and Ethan and Julie have a gestation period and start emailing ideas, and at some point, when we feel these characters are living in us, we bring everything that happened to us since the last movie, pages of material, stream-of-conscious rambling, and hole up for this intense writing and rehearsal period and get maybe a half a page of script from every 10 pages that we brought in.”

For “Midnight,” this started a couple of years ago: For months, they considered tracing a day in the lives of Jesse and Celine, who didn't come together until the last 15 minutes, right before bedtime, as parents of children often do.

That idea, too potentially unsatisfying for a series so rooted in the connection between its actors, was tossed last summer, and the three came together in Greece, where, for 10 weeks, they wrote, rehearsed, then shot the film; as with “Before Sunset,” “Before Midnight” was made in 15 days for less than $3 million.

And like “Before Sunset,” your first thought while watching is: Everyone seems a little more weathered, a little wiser and a little dumber. (“Rick is about a decade older,” Hawke said, “so he's like a lap ahead of Julie and I developmentally, and sees things with a different intensity, probably more foresight than we do, so the movies have both visions working within them.”) And your last thought is: Is that the last movie?

Delpy said nobody wanted a second film, but then they were Oscar-nominated for their screenplay, so …

Hawke said the third film “feels resolved to me in a way the others did not.”

As for Linklater?

For the past decade, for a few days each year, he has shot material with the same young actor, material that will appear in an upcoming film. So time, as his great subject, has not receded. “And yet, I am always asked by people to do a ‘Dazed 2,' ‘School of Rock 2,' and some things you want to remain themselves. I would be fine if we never did another ‘Before' film. It would not feel like we didn't accomplish something big here. That said, six years on, maybe Julie and Ethan and I get to talking, then I go, ‘Hey, you know …'”